Preliminary studies have revealed that insulin, cortisol, and somatomedin-like growth factors influence incorporation of radioactivity into chondrosarcoma proteoglycan in vitro at physiologic concentrations. An investigation will be undertaken to characterize the structure of radiolabeled proteoglycans produced under different conditions of culture. The investigation will reveal whether these growth factors induce a previously unidentified type of proteoglycan under different culture conditions or influence proteoglycan heterogeneity by affecting specific enzyme steps in proteoglycan metabolism. Isotope incorporation will be used to radiolabel newly synthesized proteoglycans. Proteoglycans secreted into the medium, remaining associated with the extracellular matrix and located intracellularly will be isolated and purified by equilibrium density-gradient centrifugation, ion-exchange chromatography, gel filtration chromatography, and affinity chromatography. Their structures will be characterized in detail using conventional procedures. Alterations in proteoglycan structure will be used to determine which steps involved in proteoglycan and glycosaminoglycan metabolism should be selected for further investigation. Conditions will be developed in this study for maintaining viable rat peritoneal and human lung mast cells in culture. Mast cell proteoglycan metabolism will then be investigated under different in vitro conditions and the structures of these molecules will be characterized in more detail than reported by other investigators using improved isolation and purification technology. The effects of immunologic activation and xyloside treatment on proteoglycan metabolism in mast cells will be studied. In addition, feedback inhibition of proteoglycan synthesis will be investigated in both the mast cell and the chondrosarcoma chondrocyte in order to gain some insight into their mechanisms or regulation of proteoglycan synthesis.